As China’s Alibaba moves closer to a record-setting U.S. stock market debut, every step the giant e-commerce firm takes is a boost for Yahoo shareholders — even as it turns up the heat on CEO Marissa Mayer’s efforts to turn around the struggling Silicon Valley company.

Yahoo’s stock rose more than 4 percent Monday, a day after Alibaba announced it will hold its initial public offering in the United States rather than Hong Kong. Yahoo owns 24 percent of the high-flying Chinese firm, a conglomerate described as a cross between Amazon, eBay and Google. and many U.S. investors view Yahoo shares as their best opportunity to place an early bet on Alibaba’s rapid growth.

But if enthusiasm for its Asian investments has fueled a sharp spike in Yahoo’s stock price over the past 18 months, analysts say the IPO will put more pressure on Mayer to deliver on a long-promised overhaul of Yahoo’s core advertising business. Yahoo is obliged to sell a large chunk of its Alibaba stake in the IPO, which should produce an infusion of cash for the Sunnyvale company but will also remove one of the key pillars that has propped up Yahoo’s stock price.

Until now, “no investor has needed to care about what’s going on in Yahoo’s core business” because Alibaba’s performance has masked Yahoo’s weakness, Pivotal Research analyst Brian Wieser said Monday. But he said the sale of Yahoo’s stake could remove much of the “air cover” that Alibaba has provided.

Yahoo’s online advertising business has slumped in recent years; annual revenue fell 6 percent to $4.7 billion in 2013, while rivals such as Facebook and Google continue to grow.

Alibaba, meanwhile, is expected to post revenue of $7.6 billion for 2013, up 55 percent from the previous year, according to analysts at Bernstein Research, who estimate Yahoo’s stake in Alibaba represents nearly 60 percent of the Sunnyvale company’s $39.5 billion stock market value.

Without Alibaba, wrote Bernstein’s Carlos Kirjner in a recent note, “we find it hard to be optimistic” about Yahoo’s core business.

Wall Street is far more upbeat about the impending IPO of Alibaba. While the company keeps a tight lid on financial details, estimates of Alibaba’s potential market value range from $150 billion to $200 billion.

That puts Alibaba in a league with Facebook, which has a stock market value of $175 billion, or Oracle, valued at $172 billion.

Depending on how its stock is priced, Alibaba could raise as much as $18.4 billion in its first offering. That would surpass the $16 billion raised by Facebook in its 2012 stock debut, which set the record for U.S. tech company IPOs. It would make Alibaba the second-biggest U.S. IPO for any sector, after the $19.6 billion raised by Visa in 2008, according to research firm Deallogic.

Yahoo owes its stake in Alibaba to a 2005 deal negotiated by then-CEO Jerry Yang, who put up $1 billion for 40 percent of the Chinese startup. The arrangement has produced returns valued at hundreds of millions of dollars for Yahoo. But over the years, Alibaba CEO Jack Ma (who is now executive chairman) sought greater independence from Yahoo and another big investor, Japanese tech company SoftBank.

After she was named Yahoo’s CEO in 2012, Mayer closed a deal to sell half the company’s stake in Alibaba for $7.6 billion, with about $3 billion returned to Yahoo shareholders through stock buybacks.

But that deal requires Yahoo to sell at least 40 percent of its remaining stake in Alibaba when the Chinese firm goes public. While that could yield $15 billion or more, Kirjner has estimated Yahoo may collect $7 billion after taxes.

That would provide a tidy return for Yahoo shareholders if the company shares the proceeds either by awarding a dividend or buying back shares, which would drive up the value of Yahoo stock. It could also give Mayer a new stockpile of cash to invest in expanding the company, through hiring, acquisitions or other initiatives, said analyst Colin Gillis of BGC Partners.

At this point, analysts agreed, it’s too early to know exactly how much Yahoo and its shareholders will make from Alibaba’s IPO. Yahoo hasn’t said how many shares it will sell, and Alibaba hasn’t announced an initial stock price or the size of its offering. It also hasn’t set a date for the IPO, although it’s expected this year.

But once the dust clears, Wieser said, investors will have a better idea of how much Yahoo’s remaining slice of the Chinese company is worth.

“And then investors will be able to express a real point of view on the value of Yahoo’s core business,” he said. “That will reinforce the scrutiny of a CEO who has been at the helm for two years.”